Research into the use of optical sensors for ultrasonic wave and acoustic emission sensing is becoming more popular. Most commonly, these sensors are fiber Bragg gratings (FBGs) that are bonded directly to a test surface. Ultrasonic waves that pass through the structure cause local expansion and compression in the fiber grating, causing a change in effective wavelength of the grating. This change in wavelength changes the grating's reflected light spectrum. Reception of ultrasonic waves using FBGs takes advantage of the ultrasonic amplitude modulation of the reflected light spectrum, which can be extracted (e.g., by using a matched grating) to provide a signal functionally equivalent to the voltage-time signal extracted from traditional sensor types (e.g., piezoelectric, magnetostrictive, etc.). The FBG sensors may be single-wavelength, π-shifted, variable wavelength (e.g. chirp), or of another design. Furthermore, the FBG sensors can be implemented in single-sensor configurations or in more complex configurations, including, but not limited to, Fabry-Perot interferometers. Advantages of FBG sensors include: use of multiple sensors (gratings of different wavelengths) along a single fiber, wide frequency bandwidth, insensitivity to EMI, minimal signal loss with long cables, reduced cable and sensor weight, and others.